The invention relates to a tensioning device for expanding a threaded bolt by a pull on its threaded end portion, with a supporting tube surrounding the threaded end portion and a nut screwed onto the threaded end portion, with a cylinder arranged in the prolongation of the supporting tube and having at least one piston movable therein in the longitudinal direction and connectable to a hydraulic supply, with an interchangeable bush screwable to the threaded end portion and designed to be drivable axially by the piston, and with a gear arrangement for adjusting the nut, components of the gear arrangement being a driver element engaging externally on the nut and a drive shaft provided with an engagement structure for a drive tool.
Bolt-tensioning devices of this type, such as are known, for example, from US 2008/0006122 A1 and WO 99/46089, serve for the tightening and, where appropriate, also the loosening of highly loaded screw connections composed of a threaded bolt and of a nut. The tensioning device has the task of applying a stipulated prestressing force to the threaded bolt for a certain time in the bolt longitudinal direction by means of a hydraulically actuated piston, in order thereby to create the possibility of tightening or retightening or also of loosening, free of torque, the nut which is screwed onto the threaded bolt. To rotate the nut, a gear with an engagement structure for an external drive tool is arranged laterally on the housing of the tensioning device. After the external drive tool has been attached, this is rotated about an axis of rotation which is arranged parallel to the longitudinal mid-axis of the piston. In practice, particularly in the case of threaded bolts arranged closely next to one another, situations often arise where the available space is not sufficient for the tensioning device, including the gear fastened laterally to it, or the engagement structure of the gear is in such an awkward location that a suitable drive tool cannot be attached there or can be attached only with difficulty.
The object of the invention is, therefore, to provide a tensioning device which makes it possible to work even in those spatially confined situations where conventional tensioning devices cannot be used.